Lisdexamfetamine

Absorption

Pharmacokinetic studies after oral administration of lisdexamfetamine dimesylate have been conducted in healthy adult (capsule and chewable tablet formulations) and pediatric (6 to 12 years) patients with ADHD (capsule formulation). After single dose administration of lisdexamfetamine dimesylate, pharmacokinetics of dextroamphetamine was found to be linear between 30 mg and 70 mg in a pediatric study (6 to 12 years), and between 50 mg and 250 mg in an adult study. Dextroamphetamine pharmacokinetic parameters following administration of lisdexamfetamine dimesylate in adults exhibited low inter-subject (<25%) and intra-subject (<8%) variability. There is no accumulation of lisdexamfetamine and dextroamphetamine at steady state in healthy adults.
Absorption
Capsule formulation
Following single-dose oral administration of lisdexamfetamine dimesylate capsule (30 mg, 50 mg, or 70 mg) in patients ages 6 to 12 years with ADHD under fasted conditions, Tmax of lisdexamfetamine and dextroamphetamine was reached at approximately 1 hour and 3.5 hours post dose, respectively. Weight/Dose normalized AUC and Cmax values were the same in pediatric patients ages 6 to 12 years as the adults following single doses of 30 mg to 70 mg lisdexamfetamine dimesylate capsule.
Effect of food on capsule formulation
Neither food (a high fat meal or yogurt) nor orange juice affects the observed AUC and Cmax of dextroamphetamine in healthy adults after single-dose oral administration of 70 mg of lisdexamfetamine dimesylate capsules. Food prolongs Tmax by approximately 1 hour (from 3.8 hours at fasted state to 4.7 hours after a high fat meal or to 4.2 hours with yogurt). After an 8-hour fast, the AUC for dextroamphetamine following oral administration of lisdexamfetamine dimesylate in solution and as intact capsules were equivalent.
Chewable Tablet formulation
After a single dose administration of 60 mg lisdexamfetamine dimesylate chewable tablet in healthy subjects under fasted conditions, Tmax of lisdexamfetamine and dextroamphetamine was reached at approximately 1 hour and 4.4 hours post dose, respectively. Compared to 60 mg lisdexamfetamine dimesylate capsule, exposure (Cmax and AUC) to lisdexamfetamine was about 15% lower. The exposure (Cmax and AUCinf) of dextroamphetamine is similar between lisdexamfetamine dimesylate chewable tablet and lisdexamfetamine dimesylate capsule.
Effect of food on tablet formulation
Administration of 60 mg lisdexamfetamine dimesylate chewable tablet with food (a high-fat meal) decreases the exposure (Cmax and AUCinf) of dextroamphetamine by about 5% to 7%, and prolongs mean Tmax by approximately 1 hour (from 3.9 hours at fasted state to 4.9 hours).
Elimination
Plasma concentrations of unconverted lisdexamfetamine are low and transient, generally becoming non-quantifiable by 8 hours after administration. The plasma elimination half-life of lisdexamfetamine typically averaged less than one hour in volunteers ages 6 years and older. The plasma elimination half-life of dextroamphetamine was approximately 8.6 to 9.5 hours in pediatric patients 6 to 12 years and 10 to 11.3 hours in healthy adults.
Metabolism
Lisdexamfetamine is converted to dextroamphetamine and l-lysine primarily in blood due to the hydrolytic activity of red blood cells after oral administration of lisdexamfetamine dimesylate. In vitro data demonstrated that red blood cells have a high capacity for metabolism of lisdexamfetamine; substantial hydrolysis occurred even at low hematocrit levels (33% of normal).
Lisdexamfetamine is not metabolized by cytochrome P450 enzymes.
Excretion
Following oral administration of a 70 mg dose of radiolabeled lisdexamfetamine dimesylate to 6 healthy subjects, approximately 96% of the oral dose radioactivity was recovered in the urine and only 0.3% recovered in the feces over a period of 120 hours. Of the radioactivity recovered in the urine, 42% of the dose was related to amphetamine, 25% to hippuric acid, and 2% to intact lisdexam …